U.S. President Donald Trump discussed a variety of global issues late Thursday in Hamburg with German Chancellor Angela Merkel, one of his frequent critics on the world stage, just ahead of Friday's start of the G-20 summit of the leaders of the world's biggest economies.

The two leaders met in a hotel, briefly greeting each other in front of reporters before heading behind closed doors for their talks. Later, a Merkel spokesman said economic and trade issues, North Korea's latest missile test and turmoil in the Middle East and Ukraine were discussed.

In recent days, Merkel has voiced her displeasure at Trump's withdrawal from the 2015 international Paris climate agreement aimed at curbing greenhouse gas emissions across the globe in the coming years. She has called Trump's decision "extraordinarily regrettable."

She also has said that Europe can no longer entirely rely on the United States as a partner on the world stage, as Trump advances his "America First" policies. Merkel has said that Germany and China can work together to resolve world issues.

For his part, Trump has been critical of Merkel's efforts to allow more immigrants to cross into Germany at a time when the U.S. leader has been defending his order to curb immigration from six majority-Muslim countries in an effort to combat possible terrorist attacks.

It is the second time the two leaders have met for face-to-face talks, with Merkel having visited the White House in Washington in March, when awkward exchanges marked their time in front of cameras.

FILE - President Donald Trump and German Chancellor Angela Merkel participate in a joint news conference in the East Room of the White House in Washington, March 17, 2017.

During a joint news conference, Trump quipped that the two leaders had something in common, a reference to Trump's unsubstantiated claim that former President Barack Obama wiretapped him during the 2016 U.S. election. The German was furious when she found out that the U.S. had tapped her calls during the Obama administration.

Merkel did not smile at Trump's attempt at a humorous recall of the eavesdropping.